Tesco, Britain’s biggest retailer, announced the cash and shares deal in January in a bid to increase its exposure to the fast growing catering sector.

The Competition and Markets Authority said on Tuesday the phase 1 investigation would run until July 25.

“During this period, the Competition and Markets Authority (CMA) will assess whether the deal could reduce competition and choice for shoppers and other customers, such as stores currently supplied by Booker,” it said.

After the first phase, the CMA could either clear the deal or refer it for a full phase 2 investigation lasting up to 24 weeks unless the merging parties offer proposals addressing any concerns. ($1 = 0.7770 pounds) (Reporting by Kate Holton, editing by James Davey)